FIG. 1 shows an example surveillance system 10 having a video camera 12, a controller 14, an alarm system 16 and a recording device 18. The camera 12 includes an imager for capturing a viewed scene and a motion detection feature, which outputs a motion signal to the controller 14 when motion is detected in the scene viewed by the camera 12. Motion detection is a desirable feature in security applications. An immediate benefit of including a motion detection feature in the camera 12 is that the feature helps save recording space by only activating the video recording device 18 (and/or only sending the detected moving region to an encoder for compression) when motion is detected. Another benefit of motion detection is that it allows the camera 12 to send an alert to the security personal in the viewing room causing them to focus on the specific area where motion has been detected. This is especially useful when there are many monitors in the viewing room that are connected to many different cameras, such as e.g., in a casino viewing room. The alarm system 16 could also be triggered by the controller 14 when motion is detected by the camera 12.
Conventional motion detection algorithms use temporal processing that compares an image of the current frame with a reference frame image and then counts the number of pixels that are different between the frames. This type of motion detection technique, however, requires a large frame buffer and, therefore, cannot easily be implemented in system-on-a-chip (SOC) imager systems, which have limited memory resources and general circuit area limitations. Moreover, the large frame memory adds cost to the imager, which is also undesirable.
Accordingly, there exists a need for an improved method and system for motion detection within an imager. There further exists a need for a motion detection system and method that may be implemented in a system-on-a-chip imager system.